“If everyone thought like me,” says María Melba Troches, “large swaths of the Amazon rainforest would still be standing.”

The oil industry has already taken over her ancestral lands in Putumayo, in south-western Colombia. Gas flaring has led to respiratory illnesses, water has been polluted and traditional lands taken away. What few jobs the industry has provided are menial and insecure, so young men are driven to the drug trade, women to prostitution. HIV rates are rising, as is crime. That, Troches says, has been the price of development in Putumayo.

Now a new highway is going to be built through the region, part of a $70bn investment programme for the Amazon led by the Brazilian Development Bank, BNDES. As Colombia prepares for significant investment in its infrastructure and natural resources, governments and companies are promising social and economic benefits for all. Troches says those benefits never come.

“Whatever they do, the money is going to go outside … It’s time to say ‘stop’,” she says emphatically.

The Iniciativa de Integracíon Sudamericana (Iirsa), the project to integrate infrastructure in South America, will link Brazil to the Pacific Ocean and branch out through the Amazon to connect Brazilian mines and agricultural companies to trade routes and power supplies. The proposals include more than 500 mega projects, including hydroelectric dams, highways, waterways, ports and gas pipelines stretching across the Amazon basin.

Troches has just arrived in Villavicencio, in central Colombia, for a congress of indigenous peoples from the Amazon. They are working to formulate a response to this new threat to their livelihoods.

Ecologically unique and critical for preventing worsening climate change, the Amazon has been a perpetual battleground for conservationists. It is also a new economic frontier for Latin American countries that have based their development on the export of natural resources.

Satellite images of the Amazon analysed by the Brazilian research group Imazon show that more than 2,750 sq km – an area twice the size of Los Angeles – was cleared between August 2012 and July 2013. After a relatively low rate of deforestation in the previous few years, the shift in gear has alarmed activists.

Topological maps show the roads spreading through the forest. The spaces around them become denuded as illegal loggers take advantage of the access routes. There is a marked correlation between indigenous people’s rights and the preservation of the forest, but now these rights are being undermined.

Brazil’s investment in the region has grown exponentially in the past five years, as it has sought to build a new political and economic bloc on the continent. Many of the companies poised to benefit from the expansion of the network are Brazilian.

Led by populist, leftwing leaders, several countries have tried to exit the US sphere of influence. This has meant tying themselves economically to other rising powers, notably China, and strengthening their relationships with one another. Iirsa is part of that process, physically linking the region and binding it tighter to its regional powerhouse, Brazil.

BNDES operates like a development bank and a trade finance organisation. It has participated in the expansion of the Brazilian mining and mineral industry worldwide as well as companies from the country’s powerful agro-industrial lobby. It has been the key investor and convener of most Iirsa projects.

The enthusiastic acceptance of Iirsa by governments that control Amazon regions has led to the rolling back of environmental obligations, threatening the already fragile rainforest. The legal advocacy group Dejusticia says a pattern is emerging across the region of governments ignoring their obligation to obtain free, prior and informed consent from local communities before embarking on extractive or infrastructure projects.

In Colombia, public companies are working around environmental laws and ignoring expert advice, according to an environmental expert who worked on the initial impact assessments for an Iirsa waterway project. She lost her job after concluding that the project would be ecologically disastrous, but was not surprised that it was progressing despite her concerns. “So much of it is done in secret,” she says.